More water than ten times the volume of all modern lakes combined

Disaster in largest lake ever

A new study reveals the rise and the fall of the largest-known megalake in the Earth’s history some 10 million years ago. The megalake fauna, which included dwarf whales and dolphins, evolved and thrived initially but were later nearly obliterated by cataclysms that repeatedly turned the region into a toxic waste-waterworld. “These crises were similar to the desiccation of lake Aral, but hundreds of times larger in magnitude”, lead author Dan Palcu (Utrecht University and University of São Paulo) explains.

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Locatie van het Paratethysmeer
Location map of the Paratethys megalake. For comparison reasons the present-day geography is shown as well.

Megalake Paratethys formed some 12 million years ago, after a giant sea disconnected from the ocean and life evolved for 5 million years cut-off from the rest of the world. "The lake contained an exotic endemic fauna that included dolphins and whales – among them, the smallest ones in the Earth history” explains Pavel Gol’din, an expert in marine mammals (lead researcher at the Schmalhausen Institute of Zoology, Ukraine) who was not involved with the study. The 3 m long Cetotherium riabinini is the best known of these dolphin-sized dwarf baleen whales.

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Dwergvinvis Cetotherium riabinini, vergeleken met een mens van 1,8 m.
Dwarf whale Cetotherium riabinini, compared with a 1.8 m human shape (Gol'Din en Lena Godlevska, Wikimedia Commons)

Larger than the Mediterranean Sea

While its inhabitants shrunk, the lake expanded to cover an area of 2.8 million km2. “That’s larger than the modern Mediterranean Sea”, says Palcu. The lake stored an estimated 1.77 million km3 of brackish water. “This represents more than ten times all the fresh and salt-water presently stored in lakes.”

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Tabel ter vergelijking van het watervolume tussen het reuzenmeer enerzijds en meren en ijskappen anderzijds.
Water volume comparison between the megalake and other waterbodies (lakes and ice-sheets)

Post-apocalyptic

During partial desiccation episodes, up to a third of the megalake water was lost to evaporation, the lake fragmented, and the central basin, now the Black Sea, became particularly toxic and barren. Most lifeforms became extinct, and those that survived were sick and deformed. “It must have been a post-apocalyptic prehistoric world, an aquatic version of the wastelands from Mad Max”, explains Wout Krijgsman (Utrecht University).

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Rotsen gevormd tijdens de rampen die het meer troffen zijn kliffen geworden met uitzicht op de Zwarte Zee, een van de weinige overblijfselen van het oude reuzenmeer. Kaap Kaliakra, Bulgarije.
Rocks formed during the megalake crises have become cliffs overlooking the Black Sea, one of the few remains of the ancient megalake. Cape Kaliakra, Bulgaria (D.V. Palcu)

Other authors include Irina S. Patina from the Geological Institute of the Russian Academy of Science, Marius Stoica and Ionut Sandric, from the University of Bucharest, Romania, Iuliana Vasiliev from the Senckenberg Biodiversity and Climate Research Centre, Germany and Sergei Lazarev from Utrecht University.

Article

Dan Valentin Palcu, Irina Stanislavovna Patina, Ionuț Șandric, Sergei Lazarev, Iuliana Vasiliev, Marius Stoica & Wout Krijgsman, 'Late Miocene megalake regressions in Eurasia', Scientific Reports https://www.nature.com/articles/s41598-021-91001-z#citeas